Original subtitles

0 Now you should have PyCharm up and running, 1

and we're finally ready to tackle today's project, 2

which we're going to write in PyCharm. You've just been hired. 3

Congratulations, but first there's the matter of coffee. 4

We all know that programmers can't work unless they're loaded up on coffee. 5

So your company has asked you to create the code for a coffee machine. 6

Now you, very cleverly, go online and look at the other coffee machines. 7

And you notice that it only costs $230 to buy a coffee machine, 8

but you're not going to cheat. You're going to create everything from scratch. 9

And luckily we don't actually have to build the hardware because we're programmers, 10

right? 11

But we're going to use this real-life coffee machine as the inspiration for our 12

virtual coffee machine, noting the features and the capabilities. 13

So what does it say? I found some wonderful graphics on here 14

which tells me that they're three hot flavors 15

which I'm guessing are these three buttons, it's coins operate 16

which I think they mean it's coin operated, and there's not much else that it can 17

do. 18

Let's take this example and we're going to make a digital version of it. 19

We're going to create our own coffee machine. 20

And the first step we need to replicate is the ability to make three hot 21

flavors. So the flavors we're going to make are 1. espresso, 22

2. latte, and 3. cappuccino. Here 23

are the recipes for these three types of drinks. 24

Each of them requires a different quantity of water, 25

a different quantity of coffee and a different quantity of milk. 26

And they also each half a different price. 27

We're going to be modeling all this data in our coffee machine program as well. 28

But luckily for you in the starting code, 29

I've already included all of this data inside a dictionary. 30

So you don't have to remember this, 31

although it might help if you're at home and you decided that you really wanted 32

a latte instead of your usual black coffee. Now, in addition, 33

the coffee machine has some resources that it has to manage. 34

So it starts out with 300ml of water in the tank, 35

200ml of milk and 100 grams of coffee. 36

The second feature of our coffee machine is that it's coin operated. 37

So we're going to be using American coins and they have four types of coins: 38

the penny, the nickel, the dime, and the quarter. 39

They used to also have the dollar as a coin 40

but a few years ago they stopped minting that. So we're not going to count it 41

and it probably means one less if statement for us. 42

Notice what each of these coins are worth. The penny is worth a cent, 43

the nickel worth 5 cents and the dime 10 cents, 44

and the quarter is a quarter of a dollar. 45

These represented in decimal values would look something like this. 46

Now here's the important part. Let's think about what our program requirements are 47

if we break it down one. 48

1. We need our coffee machine to be able to print a report. 49

It needs to be able to tell us what resources it has left, 50

how much water has left, how much milk, et cetera. 51

If you head over to the completed version of the coffee machine, 52

the link is in the course resources, 53

and you can go ahead and try out the final version of the coffee machine. 54

So let's say that we wanted a report on all the resources that the machine has. 55

All we have to do is type report, and we can see all the resources we have. 56

Now, in addition to being able to print a report, 57

we also want to be able to check that the resources are sufficient when the user 58

orders a drink. Now let's say that the user decided to order a latte. 59

It asks me to insert some coins and then it gives me the change and it gives me 60

the latte. But now if I check the report, 61

I can see that I've only got a hundred mils of water left. 62

And I know from the previous slide that a latte and a cappuccino is going to 63

need more than that amount of water. So let's see what happens 64

if I go ahead and order a cappuccino. It says, sorry, 65

there's not enough water. 66

So our program is able to look through all the resources that the machine has, 67

checks it against the recipe of the drink that we're trying to make, and tells the 68

user if there is insufficient water or if there's insufficient milk, 69

and as long as one of the resources is insufficient, 70

then it can't make the drink and it gives the feedback to the user. Now, 71

as you saw before, 72

our program also needs to be able to process coins because our machine is coin 73

operated. 74

So no fancy contactless payments or pay with your Apple watch, none of that. 75

We've only got coins. When we order something, 76

it should ask us to insert coins. 77

And it's going to ask for the quantity of each type of coin. 78

So let's say that I insert one of each, then in this case, 79

there's actually not enough money to cover my drink and it refunds the money and 80

doesn't give me a drink. But on the other hand, if I do insert enough money, 81

then it should be able to calculate how much money all of these coins are worth 82

and then calculate the amount of change based on the cost of my drink. 83

And then it should hand me my drink and tell me to enjoy. So, 84

in addition to being able to process the four types of coins, 85

calculating the actual monetary value based on the number of points, 86

it should also check that the transaction is successful. 87

That the user didn't try to hoodwink us by not giving enough coins and asking 88

for a drink. So if they haven't inserted enough coins, 89

then we're just going to refund them and tell them, sorry 90

that's not enough money, and not give them their drink. 91

But if the transaction was successful, 92

then we're going to make the coffee. And in the process of making the coffee, 93

we're going to have to deduct the resources. 94

Notice how every time we make a drink, 95

say in this time we made a latte and previous to the latte, 96

we have 300 mills of milk. But after the latte, 97

when we asked for the report, you can see that the water has been reduced, 98

the milk has been reduced, 99

the coffee has been reduced and the money has been put into the coffer. 100

This program, even though it seems simple, 101

just a simple digital version of a coffee machine, 102

it actually has quite a few requirements. 103

So I recommend that you look at the screen and try to see how each of the 104

requirements work by having a play around with the final version of the code. Now 105

I've created a detailed program specification for you as a PDF file 106

which you can download in the course resources. 107

And this goes into a lot more details on each of those points. For example, 108

what should the prompt print in the beginning of the program, 109

and then how to turn the machine off, 110

how to print the reports and how each of those points should work in detail. 111

Go ahead and download this and make sure you read each of the sections and test 112

it out in the final working version of the project. 113

Once you're ready, 114

you can go ahead and head over to the starting version of the code. And again, 115

I'm sharing this using Repl.it, 116

but I want you to copy everything that's in here, 117

there's only one file the main.py file, 118

and I want you to create a new project using PyCharm and call it coffee 119

machine, 120

Right? 121

And then create a new file inside your project called main.py, 122

and then paste all of the starting code into your main.py. 123

And now you are going to code inside this file. And once you're ready, 124

you're going to click run and you'll be able to run this main.py down here 125

and this will act as your console. Now, 126

one really handy feature of 127

PyCharm is something called to-do tracking. 128

Whereas previously in Repl.it I've been creating to-dos and you've been able to 129

view them. But if I have lots of to-dos in different places, 130

you can't actually see all of them at once. 131

You have to scroll through the file looking for them. 132

But in a professional tool, 133

we actually have something called to-do tracking and its a tab that's down here. 134

So if I go ahead and take some of these program requirements, 135

I can put them in as to-dos. To create a 136

to-do you have to follow the syntax. First is a pound sign 137

and then we write TODO in all caps, and notice how that's just changed color just 138

now, and now you can see in the todo tab, 139

it's found one todo item. 140

Now we can write todo number one 141

and this is to print a report of all the coffee machine resources. 142

Now let's say that I created a todo somewhere else, right? 143

Like all the way up here, 144

check that the resources are sufficient to make the drink order. And notice how 145

they're completely in different places in a different order. 146

But every time I create one of these todos using this format, 147

it will get picked up in the 148

todo tab. And you can go ahead and see where they live. 149

So it's found two items inside our main.py 150

and you can see that this one is todo one, this one is todo two. 151

And when you click on them, 152

they'll take you to the correct places in your code. 153

Use this to break down the problem into smaller problems that you can solve one 154

by one, 155

just as you've done before and try to see if you can complete this project. 156

Just the word of warning: this project is quite ambitious. 157

But you've now got professional tools to help you, 158

and you've got a lot more skill under your belt. 159

So give this problem at least an hour to work on it and make sure that you 160

satisfy all the criteria that's set out in the program requirements 161

and also that your program works exactly the same as the final version of the 162

coffee machine.